Phytochemical constituents and antimicrobial activity of leaf extracts of three Amaranthus plant species

This study investigated the phytochemical constituents and antimicrobial activity of hexane, ethyl acetate, dichloromethane and methanol leave extracts of Amaranthus hybridus, Amaranthus spinosus and Amaranthus caudatus. The microorganisms assayed for antimicrobial activity were: the grampositive Staphylococcus aureus and Bacillus spp, the gram-negative Escherichia coli, Salmonella typhi, Pseudomonas aeruginosae, Proteus mirabillis and Klebsiella pneumoniae and a pathogenic fungus Candida albicans. The leave extracts showed a broad spectrum anti-bacterial activity but resistance to the fungus. Commonly encountered phytochemical constituents in the leaf extracts of the three Amaranthus species included flavonoids, steroids, terpenoids and cardiac glycosides. The minimum inhibitory concentration (MIC) exhibited by A. spinosus extracts against the Salm. typhi was 129 mg/ml. The MIC exhibited by A. hybridus extracts against the tested organisms ranged between 200 and 755 mg/ml whereas that of A. caudatus was between 162.2 and 665 mg/ml. The antimicrobial properties of these plants which have been used by mankind for centuries without any signs of toxicity can be used in the traditional herbal medicines which play a very important role in primary care systems in the developing world and are becoming increasingly popular in the developed world

Antimicrobial potential of wild edible herbaceous species

Natural products, either as pure compounds or as standardized extracts, provide unlimited opportunities to control microbial growth, owing to their chemical composition and diversity. Many herb and spice extracts possess antimicrobial activity against a range of bacteria, yeast, and moulds. Because of their antimicrobial properties, they could be very useful, either as food preservatives or as natural biopesticides. In particular, extracts from wild edible herbaceous species are rich in phenolic compounds. A wide variety of phenolics derived from herbs and spices possesses potent biological activities contributing to their effect against spoilage microorganisms. Many studies have pointed out the antimicrobial properties of certain classes of phenolic compounds, such as hydroxybenzoic, coumaric, and caffeic acid derivatives, flavonoids and coumarins, catechin, epicatechin, proanthocyanidins, and tannins. Moreover, some authors studied the relationship between molecular structure and antimicrobial activity of some phenolic compounds. The antimicrobial activity of polyphenols is principally due to inhibition of some important cellular functions (nucleic acid synthesis, cytoplasmatic membrane functionality, etc.) and to disruption of membrane integrity with consequent leakage of cellular contents. This chapter reviews the most important phenol-rich wild edible herbaceous species known within the Mediterranean area, highlighting the relationship between phenolic composition and antimicrobial activity of their extracts. Moreover, the problem of standardization and safety of plant extracts is analyzed in the light of the latest literature